Impact of the Prognostic Nutritional Index on Outcomes in Native Spine Infection

Study Design. Retrospective cohort study. Objective. The objective of this study was to determine if baseline prognostic nutritional index (PNI) score could be used to predict outcomes in patients with native spine infections, including the need for operative intervention. Summary of Background Data. Nutritional status is an important, potentially modifiable risk factor, to consider in the native spine population. The prognostic nutritional index (PNI) score is a tool that has demonstrated utility as a marker of preoperative nutritional status in patients undergoing surgery, however it has not yet been studied in the context of native spine infection. Methods. Adult patients (≥18 y) with a diagnosis of spine infection from 2017-2022 were retrospectively identified. Native spine infection was defined as a diagnosis of spinal infection in the absence of prior spine surgery within 3 months of diagnosis. PNI was calculated using the equation: PNI = 10 * serum albumin (g/dL) + 0.005 Total Lymphocyte Count (/μL. Patients were stratified into high or low PNI groups based on their PNI being above or below the average, respectively. Results. There were 45 patients in the low PNI group and 56 patients in the high PNI group. Patients in the low PNI group were more likely to require surgery ( P =0.046), had more levels decompressed ( P =0.012), and were more likely to undergo two or more irrigation & debridement procedures ( P =0.016). Patients in the low PNI group were also less likely to be discharged home ( P =0.016). There was no difference in length of stay, inpatient complications, 90-day readmissions, 90-day ED visits, or 1-year reoperations between groups. Conclusion. While post-admission outcomes and inpatient complications were similar across PNI groups, PNI on admission provides useful insight into the severity of infection and predicts the need for operative intervention in patients presenting with native spine infection.